Anatomy
Deltoid
The deltoid is the rounded muscle covering the shoulder. Pain on the side of the upper arm when lifting it, however, often comes from structures underneath, such as the rotator cuff.
- Deltoid
Where is it?
It starts from the collarbone, the acromion and the spine of the shoulder blade, and attaches to the outer side of the upper arm bone. It has three parts: front (clavicular), middle (acromial) and back (spinal).
What does it do?
The middle part lifts the arm out to the side, the front part forward and the back part backward. It works as a team with the rotator cuff, which keeps the head of the arm bone centred.
Common problems
Each problem has its own detailed page: symptoms, causes, treatment and when to seek care.
How we can help
When to seek care
Book an appointment if lifting your arm has hurt for more than two weeks or pain wakes you. A deformed shoulder after a fall, sudden loss of strength, or left-shoulder pain with chest pain or breathlessness needs urgent care.
Frequently asked questions
Other areas of the body
Educational content: it does not replace an assessment. Your therapist determines the cause of your symptoms in person.